I don't remember that. Amazon directed me to another Amazon page to get my activation code, I copied it and pasted in the previous window, and I was done. The entire process of downloading and activation took about 2 hours and I was playing the game in less than 3 hours after my purchase.
Right - that game-key you got from Amazon is what you'll need to boot the game up with, regardless of what DRM the game's protected with.
Usually, after installing the game fully...
Once you try to boot the game up, you'll get a box asking for your game key. Then, you input the game key into the box for activation.